Metal tube construction



Feb. 20, 1940. c. A- HORN 2,190,788

METAL TUBE CONSTRUCTION ATTORNEYS Patented Feb. 20, 1940 UNITED STATES PATENT OFFICE 2,190,788 METAL TUBE CONSTRUCTION Application January 24, 1936, Serial No. 60,588 14 claims.; lol. 25o-27.5)

This invention relates broadly to sealed metal tubes for electrical devices and appliances. More specifically, the invention pertains to sealed metal vacuum tubes employed in the radio art, and to an improved means for supporting the electrical elements and lead-in wires within the.

metal shell or container.

The use of metal tubes has become general in the radio iield on the ground that the metal construction overcomes possible deficiencies in the glass type tubes. It is claimed, for example, that the metal tubes overcome considerable breakage both in use and in manufacture; permit more economical use' of space because of the small size of the tube, and other advantages. There are inherent diiiiculties in metal tubes, however, such as the increased danger of short circuiting between the lead-in wires and the metal of the shell, and the increase of detrimental capacity effects arising from the close positioning of the lead-in and support wires of the tube to the shell.

It is an object of the present invention, therefore, to provide an improved construction in the seal between the lead-in wires and the metal container of a radio tube or the like.

Another object of the invention is to provide a type of seal for metal tubes which permits an important reduction in the length of the stem, and consequently in the length of the radio tube, thereby permitting the manufacture of tubes of small size.

Still another object of the invention is to provide a metal tube construction in which the entire electrode unit is assembled on a single insulating stem support such as glass.

An object also is to provide a seal for metal tubes which permits a considerable reduction of detrimental inductive and capacity effects between the various conductors mounted within the tube.

An additional object is the provision of an improved process for making a tube of the metal envelope or shell type wherein the stem is formed entirely of glass appropriately sealed to the base of the metal shell.

Further objects will become apparent on consideration of the following description of embodiments of the invention which may be preferred and of the process of manufacturing the same, as Well as of the accompanying drawings, in which:

Fig. 1 is a view of the stem unit showing the exhaust tube, lead-in wires and supports in position;

Fig. 2 is a view partly in section showing the stem in position on the fixture used in the stem welding machine in connection with the modification of Fig. 7;

Fig. 3 is a plan view of the turret machine 5 employed in the welding operation, particularly in the stem welding operation;

Fig. 4 is an elevation partly in section of a rotatable head of the stem welding machine showing the stem associated with the ring or l hollow disc to which it is to be welded;

Fig. 5 is an elevation partly in section of a completed radio tube embodying my invention;

Fig. 6 is a View of a section of the base of a completed tube showing a modied combination of stem and disc;

Fig. 7 shows a further modification of the stem-disc combination; and

Fig. 8 is still another modication of the disc and stem.

In accordance with my invention I utilize the form of stem unit as described in my co-pending application Serial No. 53,848, led December 11, 1935, which is Patent 2,107,254 of February l, 1938. As described in this co-pending application, vthe various lead-in Wires are inserted in a short tubular stem having, preferably, one end flared and the other end welded in a stem-making machine to form a glass wall in which the various lead-in and support wires are embedded. This sealing operation is facilitated, and in certain constructions made more secure and eflicient, by placing a glass bead around each of the lead-in wires in the approximate plane of the weld so that the heat used in the manufacture of the stem causes both the stem end wall and the beads to flow together.

A stem made in accordance with the process of this co-p'ending application has ample area for the separation of the lead-in wires suiiicient to 40 prevent undue inductive and capacity eiects between them. Further, the construction permits formation of a stem of relatively short length so that short length tubes may be easily constructed with stems of this type, an example of which is shown in Fig. 1, wherein the stem unit is designated by the numeral I0 and the parts include the stem I I having a flared end I2 and a glass wall I3 in which are embedded the various lead-in wires I4, the support wires I5 and 50 the exhaust tube I6.

Generally speaking, the method of attaching a stem of this type to a metal shell, envelope or container such as indicated by the numeral I1 of Fig. 5, consists in interposing between 'the 55 open edge of the shell and the ared edge I2 of the stem a metal ring or disc I8. and by suitable heat welding operations sealing the disc to-both stem and shell. The stem weld between the flare |2 of the stem II and the ring I8 is accomplished on a machine/of the type basically similar to the well-known Charles `Eisler type stem-making machine.

As shown in Fig. 3, the machine 20 includes the turret 2| rotatable on the base 9 in the direction of the arrow, as shown, and on which are mounted the independently rotatable heads I, 2, 3, 4, 5, 6 and 1. These heads, in the circular motion of the turret 2|, are subjected to gas flames of varying intensity, indicated by the numeral |46, there being in the first heat four jets in opposed groups 23 of two each, then in sequence ten jets in opposed groups 24 of ve each, twelve jets in opposed groups 25 of six each, and six jets in opposed groups 26 of three each. These various jets are supplied from ap propriate pipe connections, those on the turret coming from supply pipes rising through a central header connection and distributed through the various pipes 21. The number of jets is, of cours@ arbitrary and may. be varied to suit conditions.

Power for driving the turret 2| of the stem welding machine is obtained from-the electric motor 30 which is belted to a pulley wheel 3| mounted on the stub shaft 32 which in turn drives through the gears 33 and 34 to the main driven shaft 35 lying crosswise beneath the turret and base 6. The shaft 35 is provided with the worm gears 36 and 31. The worm 36 contacts with the worm wheel 31' mounted on a stub shaft 38 on which are also mounted the sprocket gear 39 and the rubber-faced wheel 46. The sprocket gear 38 meshes with the chain 4I, which in turn meshes with sprockets 42, 43, 44 and 45 on vertical shafts 46 mounted at spaced intervals about the turret adjacent to the rotatable heads 2, 3, 4 and 5. Also mounted on these shafts are the rubber wheels 41, 48, 49 and 50 which are adapted to engage cooperating gears in the heads to bring about rotation thereof, as will hereinafter be more fully described. l

The worm gear 31 on shaft 35 cooperatingly engages a worm wheel 5| mounted on a vertical shaft and carrying an arm 52 provided with an upstanding pin 53 forming a member of a Geneva gear. The cooperating Geneva gear member 54 is of the usual construction including a disc with a plurality of radially projecting gear teeth 55 having outer concave curved edges 56 separated by radial recesses 51 in which the pin 53 is adapted to engage and cause a limited rotation of the Geneva gear 54 and the attached turret 2|. As shown in this drawing, the shaft supporting the worm wheel 5| supports also the disc 58, the periphery of which has a curvature similar to that of the concave edges 56 of the gear teeth 55 of the Geneva gear 54 and is adapted to rotate with the disc edge and gear edge 56 in contact with each other except when the pin 53 is in engagement with the recesses 51 of the gear 54, at which time the gear teeth 55 have freedom of movement by reason of the formation of the disc 58 with a cut-away portion 56 adjacent the arm 52. During one complete rotation of the disc 58 and the associated pin 53 the gear 54 is rotated one-seventh of its circumference to bring about a similar movement of the turret 2| and thereby cause movement of the rotatable heads I to 1 inclusive from any given position to the next position with reference to the heating jets 23 to 26 inclusive and other fixed parts of the machine.

Reference has been made to the rotatable heads I to 1 inclusive.l These heads are identical in construction, and hence one only need be described, such as is shown in part section of Fig. 4 of the drawings and corresponding to the rotatable head 5 in Fig. 3. Referring to Fig. 4, the head 5' is shown as including a base 66 having a cylindrical downward extension 6I passing through a base support 62 of the turret 2| and terminating in a tooth gear 63 xedly secured to the extension 6I by the key 64 and nut 65. The base supports 62 in all the rotatable head umts are extended to form depending skirts 66 enclosing the gears 63 except at the side adjacent the rubber-faced wheels 46, 41, 48, 48 and 56, as

shown in Fig. 3 of the drawings with referenceto the head 3. A suitable roller bearing is interposed between the head base 66 and the base support 62. The base 60 extends upwardly and terminates in a hollow tube or sleeve 68 having a split side with outstanding lugs 69 through which the adjusting bolt 16 is passed to vary the diameter of the sleeve. The sleeve 68 is adapted to receive the fixture 1I which consists of a short tube having an enlarged head 12, the top of which is flat and provided around its periphery with a plurality of upstanding pins 13 inwardly notched as at 14 to receive the ring I8 which forms the intermediate connection between the stem edge I2 and the envelope I1. This ring, in the form shown in Fig. 5 of the drawings and as illustrated in Fig. 4, consists of a flattened disc-like portion 15 provided with an annular ridge 16 adapted to form the weld area between the ring and shell. The ring is also provided with an inner annular groove 11 which opens downwardly (Fig. 5) and forms the inner periphery of the ring I8. The groove 11 is relatively deep so as to increase the path of heat flow from the welding ridge 16 to the sealing area at the inner edge of the groove and thus preventing softening of the glass seal in the metal welding operation. The outer periphery of the ring carries a flange |36 extending downwardly and from which the base holding tongues |66 are struck in. Within this fixture and the ring and mounted thereon, the stem unit I6 is positioned with the stem flange I2 resting on the inner wall edge |3I of the groove 11 of the ring, as shown in Fig. 4 of the drawings, and with the exhaust tube I6 extending upwardly. Means for holding the stem centrally in position is provided in a pair of clamping jaws 18 having aligned cooperating grooves adapted to seat over the exhaust tube I6 and hold the same in position. These jaws 18 `are integral respectively with the arms 19 provided with handles 86' and pivotally mounted at 86 and 8| on the base 66 of the head. The arms 19 move between the guide members 82, and these arms are also held yieldingly in closed position by means of the coil spring 83 fastened at either end to the arms 19.

Means are also provided in the position on the turret of head 5 for compressing the exhaust tube I6 in order to insure a close seal between the metal and glass, if required. 'I'hls compresas shown in Fig. 3, and terminating at its top Thishead IIiSadaptedtocontactwiththeend of the exhaust tube and may be held in any desired position by means of the lock nut 0|. The other end of the lever rod 01 is pivotally connected to connecting rod 92, which in turn is pivotally connected to the cam lever Il in the base of the machine beneath the turret. The cam lever 03 is pivotaily supported by the downwardly extending` bracket M and terminates in a roller $6 which is adapted to engage the cam 96 formed on the bottom side of the cam disc 91, which in trn is secured to the shaft 00 of the worm wheel 5|.

In employing the mechanism as above described in the welding together of the glass stem unit to the associated metal ring. the operator, in the position of the turret as shown in Fig. 3, applies in positions I and 2 of the rotatable heads the ring I0 and the stem unit I0 to the xture 1 I, centrally holding the exhaust tube by means of the jaws 18 of the hand clamp. At the position of head 3 the gear 63 of the head comes in contact with the driving chain-driven gear which causes rotation of the head, and at this point also the heat of four gas jets is applied to the rotating head. In the position of head I the heat of ten gas jets is applied, and in the position of head 5 the heat of twelve gas jets is played onto the rotating head. Toward the end of the heating period of position 5 thecam 90 causes a lowering of the screw head 90, forcing the exhaust tube I6 downwardly a predetermined distance, thus forcing the mass of glass downwardly. At this point in the movement of the turret the applied heat will have been suilicient to cause a softening of the glass are edge I2, and the pressure of the cam lever will tend to force the softened glass against the inner side of the wall I3I of groove 11 of the ring I8. At the same time the gravitational eiect and the pressure of the gas ame will tend to cause the extreme outer edge of the flange I2 to curl over the groove wall |3| so that on leaving this position 5 the flared edge of the glass stem will have taken the position relative to the wall |3| such as is shown in Fig. 5 of the drawings. A reduced heat of six gas jets is applied to the position of head 6, and in the position of head 1 the Weld is permitted to cool and removal may be made of the stem at the position of head I.

The stem with the ring attached is now in condition for connection to an electrical unit, for example, and for welding with the enclosing envelope. As applied to radio tubes, the various electrode elements such as the plate |00, grid |0I, cathode |02, and heater wires |03 are connected to the lead-in and support wires of the stem, and the electrode unit including the stem is placed in the metal envelope I1 on a welding machine. The open base of the envelope I1 includes an outwardly turned flange |04 which rests on the ring ridge 16, and between this ridge and flange the Weld is made, sealing the ring I8 to the envelope I1. The envelope may now be exhausted and the exhaust tube I6 sealed oi and the base |05 conne`cted to the ring I8 by means of the inwardly turned edge portion |06 being forced into the depressions on the surface of the insulation base |05. Also, the external terminals |01 vare connected to the lead-in wires, as shown in Fig. 5, this completing the manufacture of the tube.

Modifications of the structure of the ring may bemadesuchasshowninlligs.6,'land8ofthe drawings. In Fig. 6 there is illustrated a modiiied form in which the ring ,I I0, instead of having a deep inner groove, is provided with a relatively shallow groove III adapted to receive the dared edge of the stem II, practically the entire groove space being filled by the glass. This makes a substantial and effective seal.

In the modification of Fig. 8 the construction of the ring II2 differs from those of Figs. 5 and 6 in that the inner disc grooves are replaced by an inner flangel III, extending toward the base Ill. A purpose of the ange is to permit lowering of the stern unit with the attached electrode units, thereby decreasing the overall length of the tube above the upper base line.

In the modiiication of Fig. 'l the ring III is provided with a simplified annular recess I 5, the disc portion being offset to form an inner shoulder on which the ared edge I2 of the stem rests and between which the seal is made between the metal and the glass.

In constructing these various modiflcations as well as the preferred form, the exhaust tube and lead-in wires are protected from heat by the shields |4I attached to the arms 19.

A modified type of fixture as shown in Fig.-2 may be utilized in the formation of the weld between the stem and ring of the modification of Fig. 7. Referring to this figure, the fixture I I6 is shown ywith a separable top plate I I1 attached to the fixture by the machine screw II8 and provided with a plurality of pins IIS about its pe' riphery, as in Fig. 4. Similarly, each of these pins is cut away to form a\ledge |20, opening centrally, on which the ring |2I is adapted to rest. The flared edge I2 of the stem. II is adapted to rest on the annular inner shoulder of the ring, as shown in Fig. 2, the other mechanismA of the device -being the same as described in the preferred form of the invention. In the head of Fig. 4, as well as in this modified head of Fig. 2, it is apparent that heat may be applied between the pins as well as above them, thus accomplishing a thorough and rapid heating operation.

In forming the weld between the metal and the glass it is desirable, of course, that the coefcient of expansion from heat be approximately the same in order to avoid fracture from variation in expansion and contraction of the two substances. I have found that copper-clad steel is satisfactory for the metal when used in connection with a soft glass. By copper-clad steel I refer to steel mechanically coated with a thin layer of brass and an outer coating of copper. This unit is heat treated and cold drawn to produce the copper-coated steel. Other methods of obtaining a copper coat, such as electrolytic methods, may of course be employed, provided the coeflcient of expansion of the resultant structure is similar to that of glass. Also, other substances such as molybdenum or special alloys may be used. While soft glass is used in the stern structure, other glass-like or vitreous substances may also be employed, provided the coeflicient of expansion of the metal and insulator are substantially the same.

It is pointed out that in the completed construction of the enclosure including the metal envelope, the ring and stem, that the entire internal electrical units are supported on a homogeneous insulation unit of glass, as distinguished from supporting each conductor or metal support upon separate and spaced insulation elements. By this construction, as is clearly brought out in Fig. 5, the danger of short circuiting between the lead-in wires and supports is practically eliminated and detrimental capacity and inductive effects reduced. It is pointed out, further, that the non-planar, as distinguished i'rom the plane, alignment of the lead-in wires and supports permits, for the same number of conductors, increased separation, thereby reducing undesirable inter-capacity and inductive eiects between these conductors. The circular wire arrangement is preferable, although any other configuration of the wires, such as triangular or square, might be used.

Attention is directed also to the utility of the combination of a crown-shaped stem, ring and metal envelope, in that the axially extending space of the envelope occupied by the stem support is practically negligible. 'I'his permits a minimum length of over-all tube construction.

The embodiments shown and described pertain to radio tubes, but application of the invention may obviously be made to any electrical apparatus requiring a gas sealed metal container. Also, these embodiments may be modified and therefore I do not wish to be limited thereto except as required by the appended claims.

What I desire to claim is:

1. A tube construction comprising a tubular metal envelope closed at one end and provided with an inwardly projecting ange at the other end, a dish-shaped glass stem projecting into said envelope and hermetically sealed at its outer circumference to said ange, and a plurality of conductors sealed to and extending through said stem.

2. A tube construction comprising a tubular metal envelope closed at one end and provided with an inwardly projecting flange at the other end, a dish-shaped glass stem projecting into said envelope and hermetically sealed at its outer circumference to said flange, and a plurality of conductors sealed to and extending through said stem, said conductors being arranged in approximately circular formation whereby maximum displacement between them is secured, the thickness of the base of the stem being variable.

3. A tube construction comprising a tubular metal envelope closed at one end and provided with an inwardly projecting flange at the other end, a dish-shaped glass stem projecting into said envelope and hermetically sealed at its outer vcircumference to said iiange, and a plurality of conductors sealed to and extending through said stem, said glass and envelope flange having substantially the same coeiiicient of expansion for heat and said ange lying in a plane approximately perpendicular to the envelope axis.

4. An electric tube construction comprising a tubular metal envelope having a closed end, an inwardly and transversely projecting metal flange Welded to the open end of said envelope, said flange defining an opening in the envelope, a glass wall forming a closure for said opening, a plurality of metal conductors passing through said wall, said wall having an increased thickness adjacent each of said conductors.

5. An electric tube construction comprising a tubular metal envelope having a closed end, an inwardly projecting metal ange welded to the open end of said envelope, said ange dening an opening in the envelope, a glass wall forming a closure for said opening, a plurality of circularly arranged metal conductors passing through said wall, said Wall having an increased thickness adjacent each of said conductors, and means including a glass tube centrally positioned in said wall for facilitating removal of gases from said envelope, the metal of the flange and the glass of the wall having substantially the same coeillcient of expansion for changes of temperature. and said central tube and conductors being separated by a grooved area.

6. A tube construction comprising a tubular metal envelope closed at one end and an outwardly extending flange at the other end, a ilattened ring having an -annular ridge welded tl said outwardly extending envelope flange, said ring having an inner axially extending flange forming a central opening to said envelope, a glass wall forming a. closure of saidopening, the edges of the wall being sealed to the ange of the ring, said wall being provided with means for facilitating the removal of gases from said envelope, a plurality of conductors sealed to and extending through said wall, no three of said conductors being positioned in a common plane, an electrode assembly mounted within the envelope and connected to said lead-in wires, an insulation base enclosing the glass wall of the envelope, said ring having inwardly extending fingers entering recesses on the periphery of said insulation base to retain the same in position, and a plurality of terminals in the insulation base connected to said lead-in wires.

7. An electric tube construction comprising a tubular metal envelope having one end closed, an inwardly projecting and iiattened ring welded to the other end of said envelope, said ring being provided with an axially extending and outwardly opening groovevon the inner periphery of the ring, a glass support forming a closure for the opening bounded by the inner wall of said ring groove, a portion of the glass of the wall being molded over and sealed to the inner edge of the groove to forma gas seal, a plurality of conductors passing through and sealed in said glass wall, electrode elements mounted within the envelope on said glass wall and connected to said conductors, means in said glass Wall for facilitating removal of gases Within the envelope, and an insulation base mounted adjacent the glass wall and enclosing the same, said base being supported by holding members attached to the outer edge of said ring, and a plurality of terminals secured to said base and to said conductors.

8. A tube construction comprising a tubular metal member closed at one end, a flattened ring secured to the other end of said envelope, said ring having an inwardly projecting shoulder forming the boundary thereof, a glass stem having a ared edge sealed to said shoulder, said wall having means for permitting the removal of gases within the envelope, a plurality of conductors sealed to and passing through said stem, electrode elements mounted within the envelope and attached to said conductors, an insulation base enclosing the stem and attached to said ring, and a plurality of terminals positioned in the base and connecting to the conductors.

9. The process of making gas sealed metal tubes which consists in forming a shallow dishshaped stem including a flattened central portion and a flared edge and a tubular exhaust stem opening therethrough, applying the edge of a metal ring to the flared edge of the stem while simultaneously subjecting the contiguous contacting areas of glass and ring to heat and pressure, and welding a metal envelope to the outer edges of said ring.

l0. The process of making electric tubes which comprises forming a shallow dish-shaped stem of glass with a plurality of conductors sealed therein, applying to the edge of said stem a ring of metal while simultaneously subjecting the contacting areas of metal and glass to the com-y bined action of heat and pressure, mounting on the stem and connecting to said conductors a plurality of electrode elements forming an eleotrode assembly, enclosing said electrode assembly by a metal tube closed at one end and welded to the metal ring at the other, removing the gases from the interior of the envelope, and applying an insulation base to the envelope containing terminals connected to said conductors.

11. In a metal radio tube construction, a b aseend closure therefor comprising a attened and centrally apertured metal ring, an annular groove bounding the edge of the aperture said groove opening outwardly, a mass of vitreous material forming a closure for the aperture, and a plurality of conductors passing through and sealed in said vitreous material.

12. In a metal radio tube construction a baseend closure therefor comprising a flattened and centrally apertured metal ring, an annular groove bounding the edge of the aperture, said groove opening outwardly, forming a closure for the aperture, a plurality of conductors passing through and sealed in said vitreous material, and an exhaust tube sealed in said material.

13. The process of making a base assembly for a metal tube which comprises positioning a glass mass in the aperture of a base ring, applying heat to the glass to make the edge thereof plastic, and applying pressure to the glass to force the material closely against the aperture edge.

14. The process oi making a base assembly for a metal tube which comprises positioning a glass mass in the aperture of a base ring, applying heat to the glass to make the edge thereof plastic, applying pressure to the glass to force the material closely against the aperture edge, and blowing an exhaust opening through said wall.

CLARENCE A. HORN.

a mass of vitreous material 

